1. Field of the Invention
The invention relates to a method for operating a drive train of a motor vehicle.
2. Description of the Related Art
A drive train of a hybrid vehicle comprises a hybrid drive and a transmission. The hybrid drive typically comprises an internal combustion engine, an electric motor and an electrical energy storage means. A hybrid vehicle is capable of purely electromotive driving with the internal combustion engine switched off so that the hybrid vehicle is driven solely by the electric motor with the aid of the energy stored in the electrical energy storage means. The hybrid vehicle also is capable of hybrid driving with the vehicle driven by both the electric motor and the internal combustion engine. The hybrid vehicle also operates periodically in a recuperation mode where the electric motor is operated as a generator to charge the electrical energy storage means. A hybrid vehicle also may have a kinematic storage means or a pressure storage means, with a corresponding motor, instead of an electric motor and an electrical energy storage means.
An operating mode for the drive train of a hybrid vehicle is selected in an effort to operate the drive train in an optimum manner. This selection of the optimum operating mode takes into account the consumption of the internal combustion engine and the degree of efficiency of the electric motor and the electrical energy storage means. Additionally, the selection of the operating mode determines whether the electrical energy storage means is discharged, charged or kept at an unchanged charging level. Hence, the operating mode selection is a function of a setpoint charge state and an actual charge state of the electrical energy storage means. The actual charge state of the electrical energy storage means can be detected by measurement. The setpoint charge state of said electrical energy storage means has to be determined in some other way.
EP 1 211 121 B1 discloses charging and discharging electrical energy storage means and therefore determining a setpoint charge state of the electrical energy storage means as a function of data from a navigation apparatus. The navigation apparatus contains route information about the route to be covered by the motor vehicle and corresponding height information. In accordance with EP 1 211 121 B1, an operating mode for the drive train is determined on the basis of anticipatory route data of the motor vehicle provided by the navigation apparatus and this selected operating mode controls the charging or discharging of the electrical energy storage means of the hybrid drive. This method is complicated.
In view of the above, the object of the present invention is to provide a novel method for operating a drive train of a motor vehicle.